Computation of deep beams (wandliggers)

Minor Bend & Break CT3260 reinforced concrete

dr.ir. P.C.J. Hoogenboom
October 2024

Overview of deep beam design

1) In our mind we replace the concrete and reinforcement of a deep beam by a linear elastic material. The engineer enters the shape, supports and load into a finite element program, for example SCIA Engineer. The software computes the stresses (handout 1, p 1). The computer shows the principal directions in each finite element (handout 2). The engineer draws the stress trajectories.

2) The engineer uses the trajectories to design a strut-and-tie model (vakwerkanalogie, handout 3). Software, for example Matrix Frame, computes the forces in the strut-and-tie model. The engineer chooses reinforcement to carry the tensile forces. The connections (nodes) between struts and ties are designed with hooks and stirrups to prevent local failure (handout 4).

Alternative method

1) As above.

2) The software (SCIA Engineer) computes the required reinforcement in every finite element of the deep beam (Theory: handout 1, p 6. Code: handout 5. Practice: handout 6, last page). The engineer adds development length (verankeringslengte) and designs a reinforcing cage that can be built (handout 1, p 18).

3) Optional. The engineer enters the reinforcing bars into the software. The software checks stresses and crack widths.

Lectures

October 8, 15:45 - 17:30 hours, room 1.98, Theory.

October 11, 15:45 - 17:30 hours, room 3.98, Practical, Install SCIA Engineer in advance (Google "SCIA" and "campus"). In the lecture we will follow the instructions in handout 6.

Exam

The teacher will formulate a few questions on deep beams. The questions will be part of the CT3260 exam.